The debate about immigration in Britain is embarrassing

British Prime Minister David Cameron arrives to be interviewed by Jeremy Paxman of Channel 4 during the filming of 'Cameron & Miliband ; The Battle For Number 10' on March 26, 2015 in London, England. Getty The first televised debate ahead of the General Election in May laid bare one of the most embarrassing aspects of Britain's political discussion — immigration.

He could have asked Cameron whether he regretted setting arbitrary targets on the number of people coming to Britain, especially given that free movement of people is a fundamental right of EU member states. He could have challenged Miliband to break with the apparent cross-party consensus for lower immigration and make a positive case for what migrants bring to Britain.

Sadly, and predictably, he did not. Instead Paxman challenged Cameron to apologise for failing to reduce net immigration "to the tens of thousands" and tried to get Miliband to say whether Britain was already "full up".

Such sentiments betray the soft xenophobia of our political discourse and threaten the nascent economic recovery that whoever is in Downing Street after May will be given the task of nurturing. That, at least, is the clear implication from the Office for Budget Responsibility (OBR), the government's budget watchdog.

Here's the OBR (emphasis added):

Net migration in the year to September 2014 rose to 298,000, up from 210,000 in the year to September 2013. Our previous forecasts have been underpinned by the assumption in the ONS low migration population projections that net migration will move towards 105,000 a year by mid-2019. A reduction over time seems consistent with the international environment and with the Government's declared efforts to reduce it. But in light of recent evidence, it no longer seems central to assume it will decline so steeply. So we now assume that net migration flows will tend towards 165,000 in the long term, consistent with the ONS principal population projections. Relative to our December forecast, this raises potential output growth by 0.5 per cent over the forecast period via 16+ population growth.

What the OBR is making clear is that rising net immigration will help to grow the UK's workforce over the next few years, meaning that the economy is likely to grow at a faster pace than it otherwise would have done if the government had been able to achieve its target. In other words, failing to reduce immigration was one of the big policy successes of the Coalition government.

Moreover, this is not simply about projecting possible gains into the future. In the aftermath of the financial crisis GDP per hour worked in Britain has been stagnating:

Stagnating productivity has meant that Britain's recovery has simply been driven by people working more hours, rather than boosting the amount each employee produces. That, it turn, has been helped by growing the number of people in the workforce — a substantial chunk of which has been from migrants coming into the country seeking employment (not least from troubled eurozone countries).

The positive influence of migrants on UK growth and dynamism will be no surprise for people furnished with the available evidence. Immigrants are, on average, better educated than their UK-born peers and less likely to claim welfare.

Moreover, the idea that they push down wages and take jobs from the local population is also sorely lacking in evidence. Indeed, as this LSE paper makes clear, there appears to be no discernible effects that migrants negatively impact the opportunities or wages of native-born workers.

And yet we continue to push our politicians to pledge to keep more and more people from coming to the country, with the threat of public humiliation if they fail. The debate yesterday demonstrated that the press remains at the very least complicit in furthering this narrative.

If Britain is to grow and succeed in future, we need to move on from this damaging preoccupation. The alternative is perverse: needlessly risking future prosperity in order to propagate populist myths.